Electrostatic discharge (ESD) may cause damage to sensitive electronic devices. As such, ESD protection devices are typically provided in semiconductor structures. There are several requirements for an ESD protection device to be achieved, such as human body model (HBM) standard and machine model (MM) standard. In the HBM standard, a 2 kV level is required. In the MM standard, a 200 V level is required.
A middle-voltage NMOS structure may be applied in an ESD protection device. However, a p-type ESD (hereinafter PESD) mask is needed to achieve the HBM and MM requirements. An ESD protection device saving the PESD mask may be beneficial for manufacturing cost, etc.